[time-nuts] Ebay FE-5680A Rb: Are they that good?

Bob Camp lists at rtty.us
Sat Dec 10 10:37:07 EST 2011


Hi

If you dig into the circuit, the resolution of the DDS is indeed 7x10^-13 per LSB.

Bob


On Dec 9, 2011, at 9:51 PM, Bob Smither wrote:

> Bob Smither wrote:
> 
> <snip>
> 
>> My documentation states that the full range of adjustment is:
>>  7f ff ff ff => +383 Hz
>>  80 00 00 00 => -383 Hz
> 
> This scale factor is clearly wrong - using it and applying an appropriate correction changes the frequency way too much.
> 
> From:
> 
>  http://article.gmane.org/gmane.comp.time.nuts/9473/match=fe+5680+pin+outs
> 
> (thanks Jose!) a better estimate is 140000 / Hz.
> 
> Using data after 20 hours:
> 
>  http://www.c-c-i.com/node/155
> 
> the estimated frequency offset is 1.36E-3 Hz.  Using the above scale factor gives a correction of -190 counts.  Here is the command I used to (temporarily) program the new offset:
> 
>  2e 09 00 27 ff ff ff 42 bd
> 
> (the bd is the exclusive-or checksum of the offset)
> 
> Now I wait ...
> -- 
> Bob Smither, PhD                                   Circuit Concepts, Inc.
> =========================================================================
>   A government which robs Peter to pay Paul can always depend on the
>   support of Paul.
>   --George Bernard Shaw
> =========================================================================
> Smither at C-C-I.Com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)
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